The installation of door frames and doors in commercial buildings is generally a time consuming, expensive process. Even with preformed wood or steel door frames, which are set into place prior to the finishing of the wall in which they are used, problems arise in adjusting the precise rectangular dimensions of the door frame and in finishing the wall up to the frame. In the past, it has been necessary to install door frames prior to the final finishing of the wall so that extra care must be taken by the plasterers and painters to avoid getting plaster or paint on the door frame. This additional care also results in higher labor costs in the finishing of the building in which such conventional door frame construction is used.
In addition, most conventional door frame constructions are of predetermined specific dimensions. A number of different sized doors are used in practically every building and it is necessary to buy prefabricated door frame structures uniquely dimensioned to fit the particular door opening size which is desired for each different door. Either this course must be followed, or a custom built door frame must be made in each of the door openings. The latter approach is prohibitive, particularly for commerical construction.
It is desirable to have a door frame construction which is simple, universal for door openings of various sizes, and which may be installed by workmen having minimum skill. In addition, it is desirable to have a door frame construction which can be installed in door openings after finishing of the walls is completed to thereby effect a savings in the labor required to finish the walls around door openings.